1. Field of Invention
This invention relates to fasteners, specifically to a removable clasping fastener for reversibly linking two objects.
2. Description of Prior Art
Various fasteners have been developed which serve to reversibly attach items such as keys to a holder or central containment device, such as a key ring. Often the ring itself will allow removal of the item, such as in the case of a split-ring. In other configurations, an intermediary fastener is used to attach the item to the holder. The following is a discussion of these fasteners and their drawbacks:
All of the aforementioned fasteners are substantially produced by bending metal wire. This fabrication technology is relatively slow and expensive since each piece must be produced individually and features, such as depressions, cuts, and detents, must be done in separate steps. Because metal cannot be internally colored, colored devices in these geometries must be produced in a separate coating or anodizing step; this coating can chip or wear with time, leaving the device less than aesthetically pleasing and open to corrosive attack. Depending upon the type of metal used and the cross-sectional size of the wire, it may be possible to over-strain the fastener during use, resulting in permanent deformation. One device, depicted by RAWLINGS in U.S. Pat. No. 2,209,475 (1940), is unsuitable for directly attaching the object to the containment device and therefore must use an intermediary device, such as a chain and split-ring. Because the opening loop of all of these devices is essentially two-sided, all of these designs may unexpectedly open upon the application of the torsional or twisting force commonly seen during normal usage.
U.S. Pat. No. 2,342,078 to JONES (1944) avoids some of the problems encountered with metal wire by using a die-blanked and bent sheet metal geometry. Furthermore, this design teaches the use of three interdigitating arms in the opening loop to resist torsional forces. Although not made using wire, this device nevertheless requires at least two steps for production. Likewise, the use of metal is problematic for other reasons, such as the need for coating, potential for corrosion and deformation, and high tooling costs, as delineated above. The interdigitating 3-arm geometry provides improved torsional resistance; however, the two arms on one side of the loop are not connected except at the base and therefore might be prone to separation or permanent deformation under high loads. Finally, the non-opening loop of this fastener is substantially flat and narrow and therefore the potential arises during compression for this loop to pinch the key or other object to be attached, particularly when this fastener is small in size relative to the object.